The primary objective of this proposal is to characterize the cell surface and extra-cellular carbohydrates of developing chick embryonic tissues and to study their role in cell differentiation. A variety of embryonic tissues will be analyzed for changes in complex carbohydrates during in vivo development and during dedifferentiation in tissue and cell cultures. Primary emphases will be directed toward the mucopolysaccharides and the glycoproteins, but analyses of all cellular carbohydrates, including glycolipids, glycogen, and carbohydrate pools, will be carried out.